Pulmonary infectionslecture 3

Pulmonary infectionsPredisposing factors1- Impairment of defense mechanisms * Loss of cough reflex (coma,anaesthesia,drugs---etc) * Injury to mucociliary action (smoking,viral,genetic— etc) * interference with the phagocytic or bactericidal action of alveolar macrophages. * pulmonary congestion & edema. * Accumulation of secretions (bronchial obstruction) 2- lower host resistance (chronic diseases, immunologic deficiency, chemotherapy.

3- Virulent infection.

Pneumonia Acute Inflammation & consolidation of lung parenchyma due to infectious agent.

Classification of Pneumonia By clinical setting ( Community acquired vs. hospital acquired (nosocomial) infection.

By etiology & organism (pneumococcal, viral, etc )

By morphology (lobar pneumonia, bronchopneumonia, interstitial)

Pathology1. Alveolar pneumonia

a. Lobar pneumonia Streptococcus pneumonia

b. Bronchopneumonia Streptococcus pneumonia Hemophilus influenza Staphylococcus aureus

2. Interstitial pneumonia Viral, Mycoplasma pneumonia,

Lobar pneumonia:(inflammatory exudates in alveoli lead to lobar consolidation)

Pathology of lobar pneumonia:4 phases: CongestionLasts < 24 hours: Alveoli filled with fluid and bacteria. Red hepatization• Firm red, liver-like and airless appearance of lung.• massive exudation with neutrophils, red cells, and fibrin filling the alveoli.• Pleura: Fibrinous exudate Grey hepatizationLess hyperaemia.Macrophages, neutrophils + fibrin Resolution-Lysis and removal of fibrin via sputum, lymphatics, ingested by macrophages or organized by fibrosis.

Bronchopneumonia:• Infants + young children and the elderly.• Usually secondary to other conditions associated with decrease local and general defense as- viral infections- aspiration of food or vomits-obstruction of a bronchus (foreign body or neoplasm)-chronic debilitating diseases, malnutrition

Gross:- Patchy suppurative consolidationLM:- suppurative neutrophil - rich exudate that fills bronchi, bronchioles & adjacent alveoli.

Complications of lobar pneumonia1. Abscess formation2. Empyema (pus in the pleural cavity3. Failure of resolution intra-⇒alveolar scarring (fibrosis or organization

⇒ permanent loss of ventilatory function of affected parts of lung.4. Bacteraemia:- Infective endocarditis- Cerebral abscess / meningitis- Septic arthritis

Atypical pneumonia :-

Acute febrile respiratory disease characterized by:-Patchy inflammation confined to alveolar septa.

The term atypical indicate:--No consolidation & alveolar exudate.- Inflammation confined to alveolar surface.-Moderate amount of sputum.

Causes:-Viral, Mycoplasma pneumonia, Chlamydia pneumonia.

interstitial lymphocytic infiltrates. Note that there is no alveolar exudates.Thus, the patient with this type of pneumonia will probably not have a productive cough.